Loud-speaker



Jan. 1, 1946. GRAHAM v 2,392,143

- LOUDSPEAKER 1 Filed Nov. 30, 1942 Zmventor Patented Jan. 1, 1946UNITED STATE noun-SPEAKER Maxim L. Graham, Indianapolis, Ind., assignorto Radio Corporation of America; a corporation of Delaware ApplicationNovember 30, 1942, Serial No. 467,469

7 Claims.

This invention relates to loudspeakers of the dynamic type, and moreparticularl to the diaphragm and voice coil assembly thereof,

Loudspeakers of this typehsually include a magnetic structure formedwith an air gap in which is located a flange or skirt secured to thediaphragm and upon which the voice coil is wound. One of thedisadvantages of conventional constructions is that, unless the voicecoil is properly, centered in the air gap, it frequently rubs againstthe pole pieces of the magnetic structure during vibration of thediaphragm, and this usually results in short-circuiting of the turns ofthe coil. Under certain conditions, it is also desirable that the voicecoil be protected from exposure to the atmosphere. For example, inloudspeakers used on board ships, the voice coils frequently areattacked by the sea air and they are rendered unsuitable for use.

The primary object of my present invention is to provide an improvedloudspeaker which will not be subject to the aforementioneddisadvantages.

More particularly, it is an object of my present invention to provide animproved loudspeaker of the type set forth wherein the voice coil is somounted that it will not only be protected from the atmosphere, but willalso be protected from contacting the pole pieces during vibration ofthe diaphragm.

Another object of my present invention is to provide, in a loudspeakeras aforesaid, an improved diaphragm and voice coil assembly.

Still another object of my present invention is to provide, in adiaphragm for dynamic loudspeakers, an improved mechanical connectionbetween the diaphragm and the voice coil.

It is also an object of my present invention to provide an improvedloudspeaker as aforesaid which is simple in construction, inexpensive incost. and highly efllcient in use.

In accordance with this invention, the diaphragm may comprise a central,vibratile portlon having 2. depending flange, and a peripheralsuspension also having a depending flange, the two flanges beingconcentric'and spaced slightly from each other to provide a channelwithin which the voice coil is disposed. The voice coil may be securedto the diaphragm by cement or in any other suitable manner to protect itfrom the atmdsphere. when the diaphragm is mounted in place, the flangesare disposed in the air flanges may all be molded out of suitablematerial in one piece. According to another form of the invention, thevibratile portion together with its flange may be molded together toconstitute one unitary member, the suspension and its flange may bemolded together to constitute a secondary unitary member, and the endsof the two flanges may be cemented or otherwise suitably secured to eachother to provide one integral structure.

The. novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The invention it--self, however, both -as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description of two embodiments thereof,when read in connection with the accompanying drawing, in which Figure lis a fragmentary, central, sectional view of a dynamic loudspeakerhaving a diaphragm and voice coil assembly according to one form of myinvention, and

Figure 2 is a similar view showing a modified form of diaphragm andvoice coil assembly formed in accordance with the present invention.

Referring more particularly to the drawing, wherein similar referencecharacters designate corresponding parts throughout, there is shown adiaphragm having a central, vibratory portion l formed with a dependingannular flange 3 extending in the axial direction. The diaphragm issupported by a peripheral suspension 5 which may be formed with one ormore corrugations 'l in well known manner and which is provided with adownwardly extending flange 9. The flanges l and 9 are concentric andare spaced slightl from each other to provide a channel or groove lltherebetween in which a voice coil i3 is mounted, the flanges 3 and 8being connected at their lower ends. The diaphragm I, the suspension -5,and the flanges 3 and 9, together with their connecting portion, may bemolded as one unitary, integral structure out of paper, synthetic resin,or the like, or it may be pressed out of thin sheet metal, or any othersuitable material. The voice coil may be wound separately and thencemented into the channel II with cement or the like 2| which completelycovers it. If desired, the voice coil it may be secured to the diaphragmwith the aid of a resinous cement by heating or baking whereby thediaphragm and voice coil assembly gap and protect the voice coil fromthe polepieces. According to this form of my invention, the vibratileportion, the suspension is made into one, integral structure.

The diaphragm may be supported for vibraand the tory movement in wellknown manner at the suspension I. the flanges 3 and I extending into theair gap ll of a suitable magnetic structure comprising an inner polepiece I! and an outer, annular pole piece is, as is well known in'theprior art.' It will be noted that the voice coil is is sandwiched inbetween the flanges 3 and 8 which protect it from contact with the polepieces I! and is. At the same time, the cement or the like 2| whichsurrounds the voice coil l3 and which serves to connect it to thediaphragm protects the voice coil from attack by the atmosphere or otherforeign matter.

In some cases, it may be desirable to make the diaphragm and thesuspension of two separate units as shown in Fig. 2. In thismodification, the diaphragm I and its flange 3 are made as one unitarymember separate from the suspension I and its flange 8 which constitutea second unitary member. The flange .8 may be formed at its lower endwith an outwardly extending oflset portion 23, and the flange 9 is madeat its lower end with an inwardly extending oflset portion 25 whichoverlaps the portion 28. The flanges 3 and 9 are secured to each otherat their lower ends in concentric but slightly spaced relation with eachother to provide the channel Ii therebetween, as in the modification ofFig. 1. In assembling this form of diaphragm and voice coil, the voicecoil is first wound on the outside of the flange 3 and is securedthereto by a suitable cement or the like. The suspension is then appliedto the assembled portion l and the voice coil I3 whereby the coil Itbecomes confined between the two flanges 3 and 9. The entire assemblymay then be baked to provide a substantially integral unit.

AlthoughI have shown and described but two embodiments of my invention,it will be apparent to those skilled in the art that many othermodiflcations thereof, as 'well as changes in the ones described, arepossible within the scope of my invention. I therefore desire that thisinvention between said vibratile portion and said suspension andconstituting a connection therebetween, and a voice coil secured to saiddiaphragm within said channel.

2. In a loudspeaker, an acoustic diaphragm comprising a central,vibratile portion and a peripheral suspension therefor, said vibratileportion and said suspension each including an annular flange, saidflanges being disposed in spaced shall not be limited except insofar asis made necessary by the prior art and by the spirit of the appendedclaims.

I claim as my invention: 1. In a loudspeaker, an acoustic diaphragmcomprising a central, vibratile portion and a peripheral suspensiontherefor spaced radially from said vibratile portion, means providing achannel relation to each other and being connected at their ends wherebyto provide a. channel therebetween, and a voice coil secured to saiddiaphragm within said channel.

3. In a loudspeaker, an acoustic diaphragm comprising a central,vibratile portion and a peripheral suspension therefor, said vibratileportion and said suspension each including an annular flange, saidflanges being disposed in closely spaced, concentric relation and beingconnected at their ends whereby to provide a narrow, annular channeltherebetween, and a voice coil secured to said diaphragm within saidchannel.

4. The invention set forth in claim 3 characterized in that saidvibratile portion, said suspension and their respective flanges are allformed of one unitary member.

5. The invention set forth in claim 3 characterized in that saidvibratile portion and its flange are formed of one unitary member,characterized further in that said suspension and its flange are formedof another unitary member, and charterized still further in that saidmembers are united'into one integral structure. I

6. The invention set forth in claim 3 characterized in that said flangesare formed with offset portions at their ends, and characterized furtherin that said flanges are connected to each other at said offsetportions.

7. In a loudspeaker, an acoustic diaphragm comprising a central,vibratile portion including an annular flange thereon extending in anaxial direction and a peripheral suspension concentric therewith andalso including an annular flange, said last named flange beingconcentric with and spaced slightly from said first named flange andsaid flanges being connected to each other at their ends whereby toprovide a narrow, annular channel therebetween, and a voice coil securedto said diaphragm within said channel.

MAXIM L. GRAHAM.

